Adiabatic Pumping of Orbital Magnetization by Spin Precession

TL;DR

This paper introduces a method for adiabatic pumping of orbital magnetization driven by spin precession, revealing topological effects and potential for dissipationless charge current in magnetic topological insulators.

Contribution

It presents a novel mechanism linking spin precession to orbital magnetization via topological electronic phases, including boundary effects and inhomogeneous spin textures.

Findings

Magnetization proportional to spin cross precession for small angles

Maximum magnetization reaches e/T in antiferromagnetic topological insulators

Inhomogeneous spin textures induce dissipationless charge currents

Abstract

We propose adiabatic pumping of orbital magnetization driven by coherent spin precession, facilitating the rectification of this precession. The orbital magnetization originates from the adiabatic evolution of valence electrons with a topological bulk contribution expressed as a Chern-Simons form. When the precession cone angle of spin $\mathbf{S}$ is small, the resulting magnetization is proportional to $\mathbf{S}\times \dot{\mathbf{S}}$, contributing to the magnon Zeeman effect. With a large cone angle, the magnetization can reach its natural unit, $e/T$, in an antiferromagnetic topological insulator with $e$ as the elementary charge and $T$ as the precession period. This significant magnetization is related to the global properties of the electronic geometric phases in the parameter space spanned by $\mathbf{S}$ and momentum $\mathbf{k}$. When the pumped magnetization is inhomogeneous, induced by spin textures or electronic topological phase domains, a dissipationless charge current is also pumped. At last, we discuss the boundary contributions from the spin-driving edge states, which are intricately linked to the gauge-dependent quantum uncertainty of the Chern-Simons form.